Income Taxes - Changes in Deferred Tax Asset Valuation Allowances (Detail) - Valuation Allowance of Deferred Tax Assets - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Line Items]
Balance at the beginning of the year	$ (107,174)	$ (87,623)	$ (16,599)
Charged to provision for income taxes:
Other state valuation allowances	(23,790)	500	(1,050)
Other federal valuation allowances	(247)	(477)	(511)
Rabbi trust valuation allowance	2,304	(1,066)	3,494
Other	0	(34)	0
Balance at the end of the year	(125,134)	(107,174)	(87,623)
State
Charged to provision for income taxes:
Net operating loss carryforwards	(11,612)	(17,374)	(30,457)
Federal
Charged to provision for income taxes:
Net operating loss carryforwards	$ 15,385	$ (1,100)	$ (42,500)